We considered FOUR things in the game to be a boss. There are parts of the game that give you an "End of Level" challenge, such as Z.I.M.O.N.'s color game, but they aren't boss material. I also never did consider the enemy 'Raphael' to be a boss, given his extremely limited move-set.

Here are the cards that you can pick from when you level up in the game. This list is somewhat important as each card actually gives you TWO stat increases eventually, and you can plan for what you want by looking at this list.

Also note that you can't just "Eventually get every card". Sorry, it doesn't work like that. Too many cards, not enough levels.

If you're playing solo, you can just plain skip Sparkles. The most important cards to get are Tankko and Steve. Once you have those, everything else is secondary.

Description: To unlock the specified Achiement, complete the following tasks. To view your Achievements and Stats in Steam, select "Community", then "My profile", then "View all my games", then the game and view stats.